Rev counter drops to zero and clock display goes off when I switch on my headlights.....

Just add the new earth from cluster to earth claw near the fuse box, go very carefully with the blue plastic circuit board on the back of the cluster and fingers crossed…  With the cluster still out, plug the electrical connector in and test everything as it's easy to stop a bulb from working and it's cluster out again.  

This might be a stupid question but don’t I need to re-attach the battery negative to test the connector? I just followed the guide that said to disconnect it but maybe that’s being overly cautious?
Or is there a way to test without re-connecting battery?

Is it documented anywhere what I should measure each pin for?

I’ve run an Earth to the frame at the back behind the cluster, as per Brian’s suggestion. There is SO much already going on around my fuse box, I’ll be happy for any cable I don’t need to put down there

before you cut into your original wiring, try this. get a wire and earth one end, stuff it carefully into the back of the brown wire pin on cluster.

if it fixes it, then great, you have a break in the brown wire somewhere. if not, its the cluster. or maybe the pin is loose in the plug. if you open the flap on the rear of the plug all the pins just pull out, clean them up and tweak till they make nice contact with the copper pads on the clocks.

watch out for the red wire, its permanent live so dont let it short anywhere else you'll pop the fuse. you could just remove the fuse though to kill power to it while you're working

oh well, you've already done it

when you make this connection just be aware that the MFA stalk also earths via the spade near the fusebox you were messing about with. so if you tap an earth in like this the stalk will only work if the brown wire from cluster all the way to the spade then the 2nd wire from that spade all the way back to the stalk is intact

Argh, where does the MFA stalk earth run? No idea if that cable is in tact but I can tell you that the MFA stalk isn't working, as in I only ever see the clock and it doesn't display anything else when I push the button to scroll through…

If it's accessible whilst the cluster is out, could I just tap into that MFA stalk earth too and earth it to the same new earth point I created for the cluster? I kind of figured this would fix the MFA not scrolling too… are there other things to test for that whilst the cluster is out?

Also, I'm still not clear: can I reconnect the battery negative to test all this? Otherwise how would I know if what I've done is working until I've put everything back in?!

Thanks

the cluster and stalk earths both run to the male spade you were messing with yesterday

so, if you tap an earth into the cluster brown thats fine, so long as this wire isnt broken somewhere along the way. if it is, the mfa stalk wont have an earth any more if the male spade isnt earthed. hope that makes sense…


engine ————-[spade]—————– clocks
                                         \————— mfa stalk

Can I link the battery back up to test everything when I've done the wiring?

I guess there's two wires that have to be in-tact to make the MFA work:

1) earth on connector (pin 2) —> spade by fuse box (the existing wire that I'm splicing into to earth the cluster)

2) earth on MFA stalk —> spade by fuse box

Item 1) I could resolve by running another earth to the spade by the fuse box but I tried that yesterday to no avail so I'm thinking item 2) might be the problem. So my question is, can I just splice into the earth from the MFA stalk and run it to the new earth I've created behind the cluster (or anywhere else really).

What I don't know is where that earth from the MFA stalk can be found…

assuming the wiring inside the dash is good, just adding an earth to the brown wire to chassis will be fine, i.e. dont cut it, strip the insulation and solder/crimpo a wire to it. this will also earth the mfa stalk

if there is a problem, simply find the 2/4 pin plug for mfa stalk and add an earth to the brown/white wire on the car side of the plug as well then they both have earths, all is fine.

for now if you;'re happy with your earth, hook the battery back up and try it. if the MFA doesn't cycle with ignition on, then worry about the mfa stalk earth

from the factory, the mfa stalk and cluster wires both run thru dash loom and are crimped together in the male spade with the red plug housing you were messing with the other day. then from there, you have a brown/white wire in the engine harness that goes to the side of the head.

so. if you have lost this earth on the male spade above, then cut the cluster brown wire and earth it to the chassis, this means your mfa stalk doesnt have an earth.

if you dont cut but instead add an earth to this brown wire, so long as the brown is fine to male spade, and wire from male spade to mfa stalk is also ok, then this works fine the stalk will also be earthed by the wire you added.


I'm making it sound way more complicated than it is

Ok, I wasn't going to cut the earth wire from the number 2 pin on the connector - was going to use a splice on that existing cable (like this one in the pic) to add an additional earth if that makes sense?

I guess what you're saying is - even with the additional earth in place - the MFA earth connection hinges on the existing wire from pin2 to space connector being in-tact. I will hopefully be able to give this a go this evening.

I'll hook the battery back up when I've done the earth splice.

Thanks

that'll be fine yep (even though those connectors are the devils work)

I can't solder - is there a better way?

go ahead and use one of those crimp blocks, it'll do you fine.

I'm just a wiring OCD snob. even the thought of you cutting into and soldering an unmolested VW dash loom gives me great pain and sorrow

I'd love to have you over for an afternoon to live out your OCD on all the wiring in my car:

• Aftermarket stereo added
• Aftermarket alarm and immobiliser added
• Aftermarket remote central locking system added.

I've seen a bunch of cables that are literally only connected by being twisted together - I don't even know what to do with that!

On that note, though, I have a bunch of those wire joining crimps (little red tubes) but I don't make much of them. Any suggestions as to what to use to join together two cable ends that looks neat and stands the test of time.

Cheers

a well crimped butt joint is fine (red thingy), VW use them all the time albeit high quality AMP versions crimped with a special tool

Well, I can't say that I enjoyed that much but it appears to have worked!

Did Brian's "plumbing" bits but ultimately discovered that the pins on the white 14 pin connector on slots 1 and 2 were slight ben upwards, struggling to make contact. So I gently bent them back with a toothpick and that seemed to do the trick.

However, the MFA still isn't scrolling   , so I'm on to the next challenge. I push the button on the end of the stalk and it just doesn't do anything - neither on setting 1 nor 2. Would this be symptomatic of the earth to the MFA being faulty?

rubjonny you mention a "2/4 pin plug for mfa stalk" - would that be located somewhere behind the cluster also or where should I hunt for that?

Many thanks for your help and bearing with me this far!

Ben

if you look under the knee bar (its a cabrio right?) theres a little bit of wiring coming out the base of the MFA stalk which goes to a 2 or 4 pin plug. the brown/white wire on the car side is the earth for the mfa stalk and the red/white is the 'mode' button which changes thru the mfa functions. If you earth the red/white wire with ignition on mfa should change, simply looping a wire between the red/white and brown/white should do the trick.

if it does, wiring is ok your button is bad. if not, wiring or cluster fault

Thanks John. This might be a dumb question but what is classed as the 'car side' of a connection?

the plug which is on the car loom, not the plug which is on the stalk

Is this the one? I can’t see much in there that’s  not part of a loom / has a connector….

Cheers